Magnetic tape cartridge having a brake

ABSTRACT

A magnetic tape cartridge includes a cartridge casing and a single reel which is contained in the cartridge casing for rotation. A brake component including brake member is provided with a brake gear and is movable up and down between an operative position where the brake gear prevents rotation of the reel and a retracted position where the brake gear permits rotation of the reel. The brake member has an engagement surface which is conically inclined with respect to the axis of rotation of the reel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. application Ser. No. 10/086,245, filed Mar.4, 2002 now U.S. Pat. No. 6,563,671, which is a divisional of U.S.application Ser. No. 09/220,336, filed Dec. 24, 1998; the above notedprior applications are all hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a magnetic tape cartridge, and moreparticularly to a magnetic tape cartridge comprising a cartridge casingand a single reel around which a magnetic tape is wound and which iscontained in the cartridge casing for rotation.

2. Description of the Related Art

There has been known a single reel magnetic tape cartridge, comprising acartridge casing and a single reel around which a magnetic tape is woundand which is contained in the cartridge casing for rotation, as arecording medium for an external storage for a computer and the like.Such a single reel magnetic tape cartridge is used for retainingimportant data of a computer or the like and accordingly is arranged sothat trouble such as tape jamming does not occur and the magnetic tapeis not accidentally drawn out.

The reel is provided with a cylindrical reel hub having a closed bottomand stopper gear teeth are formed in a circle and a brake memberprovided with a brake gear which is adapted to be brought intoengagement with the stopper gear teeth is disposed to be movable in thedirection of thickness of the cartridge casing along the axis ofrotation of the reel. The brake member is urged, for instance, by acoiled spring toward a position where the stopper gear teeth are engagedwith the break gear to prevent rotation of the reel when the magnetictape cartridge is not used. When the magnetic tape cartridge is loadedin a recording and reproducing system, a brake release spindle of therecording and reproducing system pushes upward the brake member todisengage the stopper gear teeth from the brake gear.

However if a space is formed between the brake member and the reel hubwhen the brake member is moved upward, dust and dirt can enter theinside of the cartridge casing through the space.

SUMMARY OF THE INVENTION

In view of the foregoing observations and description, the primaryobject of the present invention is to provide a magnetic tape cartridgein which dust and dirt can be prevented from entering the inside of thecartridge casing when the brake member is moved upward to permitrotation of the reel.

In accordance with the present invention, there is provided a magnetictape cartridge comprising a cartridge casing, a single reel around whicha magnetic tape is wound and which is contained in the cartridge casingfor rotation, the reel having a reel hub in the form of a cylindricalmember which has a bottom wall and is provided with an opening and astopper gear formed on the bottom wall, and a brake member which isprovided with a brake gear and is movable up and down between anoperative position where the brake gear is brought into engagement withthe stopper gear to prevent rotation of the reel and a retractedposition where the brake gear is disengaged from the stopper gear topermit rotation of the reel, the brake member being normally urgedtoward the operative position and moved to the retracted position by apusher member of a tape drive system which acts on the brake memberthrough the opening in the reel hub when the magnetic tape cartridge isloaded in the tape drive system,

wherein the improvement comprises that

a continuous wall portion is erected around the opening in the reel hub,and

the brake member comprises a horizontal portion which is disposed abovethe opening in the reel hub and receives force from the pusher memberwhen the brake member is moved to the retracted position and acontinuous skirt portion which extends downward from the horizontalportion and is in contact with the continuous wall portion of the reelhub, thereby closing the opening together with the horizontal portion,the brake member being moved between the operative position and theretracted position with the skirt portion kept in contact with thecontinuous wall portion of the reel hub.

It is preferred that the brake member comprises a first member and asecond member which abuts against the first member from above and ismovable up and down together with the first member, said horizontalportion and the skirt portion are formed on the first member and thebrake member is urged toward the operative position by a spring meanswhich acts on the second member.

The skirt portion may be fitted either on or in the continuous wallportion.

In the case where the brake member comprises the first and secondmembers, it is preferred that the first and second members abut againsteach other by way of a projection and the first and/or second members beformed of low friction hardwearing material.

In the magnetic tape cartridge of the present invention, the skirtportion is kept in contact with the continuous wall portion on the reelhub to keep the opening closed even when the brake member is in theretracted position, entrance of dust and dirt into the cartridge casingthrough the opening can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a magnetic tape cartridge inaccordance with a first embodiment of the present invention,

FIG. 2 is a side view of the first member of the brake member,

FIG. 3 is a side view of the second member of the brake member,

FIG. 4 is a fragmentary cross-sectional view showing an important partof the magnetic tape cartridge of the first embodiment,

FIG. 5 is a fragmentary cross-sectional view showing a modification ofthe first embodiment,

FIG. 6 is a view similar to FIG. 5 but showing another modification ofthe first embodiment,

FIG. 7 is a cross-sectional view of a magnetic tape cartridge inaccordance with a second embodiment of the present invention in a statewhere the magnetic tape cartridge is not used,

FIG. 8 is an exploded perspective view showing 15 the reel stoppermechanism of the magnetic tape cartridge,

FIG. 9 is a fragmentary cross-sectional showing the magnetic tapecartridge in a state where it is used,

FIG. 10 is a fragmentary cross-sectional showing a modification of themagnetic tape cartridge of the second embodiment,

FIG. 11 is a view similar to FIG. 8 but showing the reel stoppermechanism in a magnetic tape cartridge in accordance with a thirdembodiment of the present invention,

FIG. 12 is a cross-sectional view of a magnetic tape cartridge inaccordance with a fourth embodiment of the present invention in a statewhere the magnetic tape cartridge is not used,

FIG. 13 is an exploded perspective view showing the reel stoppermechanism of the magnetic tape cartridge,

FIG. 14 is a fragmentary cross-sectional showing the magnetic tapecartridge in a state where it is used,

FIG. 15 is a fragmentary cross-sectional view showing an example of thethrough hole and the push rod employed in the fourth embodiment,

FIGS. 16A and 16B are fragmentary cross-sectional views showing anotherexample of the through hole and the push rod employed in the fourthembodiment,

FIG. 17 is a fragmentary cross-sectional view showing still anotherexample of the through hole employed in the fourth embodiment,

FIG. 18 is a fragmentary cross-sectional view showing still anotherexample of the through hole and the push rod employed in the fourthembodiment,

FIG. 19 is a fragmentary cross-sectional view showing still anotherexample of the through hole employed in the fourth embodiment,

FIGS. 20 and 21 show modifications of the brake release member,

FIGS. 22A and 22B are cross-sectional views showing modifications of theshapes of the push rod and the through hole,

FIGS. 23A and 23B are cross-sectional views showing modifications of theshapes of the push rod and the through hole,

FIG. 24 is a cross-sectional view of a magnetic tape cartridge inaccordance with a fifth embodiment of the present invention in a statewhere the magnetic tape cartridge is not used,

FIG. 25 is an exploded perspective view showing the reel stoppermechanism of the magnetic tape cartridge,

FIG. 26 is a cross-sectional view of a magnetic tape cartridge inaccordance with a sixth embodiment of the present invention in a statewhere the magnetic tape cartridge is not used, and

FIG. 27 is an exploded perspective view showing the reel stoppermechanism of the magnetic tape cartridge.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, a magnetic tape cartridge 1 in accordance with a firstembodiment of the present invention comprises a single reel 4 aroundwhich a magnetic tape 20 is wound and is contained for rotation in acartridge casing 7. The reel 4 is formed by bonding together a lowerreel half 5 and an upper reel half 6 by ultrasonic welding. Thecartridge casing 7 is formed by fastening together upper and lowercasing halves 2 and 3 by screws and the like.

The lower reel half 5 comprises a cylindrical hub 23 and a flange 24which are integrally molded from synthetic resin. A reel plate 8 formagnetically connecting a drive mechanism of a recording and reproducingsystem is mounted on the outer bottom surface of the hub 23. Further onthe inner bottom surface of the hub 23, is formed a stopper gear 23Awhich is brought into engagement with a brake gear 32A formed on a brakemember 30 to be described later and prevents rotation of the reel 4 whenthe magnetic tape cartridge 1 is not used. The hub 23 is provided withan opening 23B, through which a brake release spindle in the recordingand reproducing system is inserted to push upward the brake member 30.An annular groove 23C in which the brake member 30 is fitted is formedaround the opening 23B.

The brake member 30 comprises a first member 31 having an annularprotrusion 31A (FIG. 2) which is fitted in annular groove 23C of thereel hub 23 and a second member 32 having an annular protrusion which isprojected downward as shown in FIG. 3. The brake gear 32A is formed onthe lower end face of the annular protrusion of the second member 32. Aprojection 31B is formed on the upper surface of the first member 31 andthe second member 32 rests on the projection 31B as shown in FIG. 4.Further an exposed portion 31C which is exposed outward through theopening 23B of the reel hub 23 as shown in FIG. 4 is formed on the lowersurface of the first member 31. A projection 32B which is like a crossin cross-section and is normally held in a groove 2A which is like across in cross-section and is formed on the inner surface of the uppercasing half 2 is provided on the upper surface of the second member 32.

The brake member 30 is urged downward by a coiled spring 10 fitted onthe projection 32B and is positioned in the cartridge casing 7 with theannular protrusion 31A of the first member 31 received in the annulargroove 32C of the reel hub 23, with the brake gear 32A and the stoppergear 23A in mesh with each other and with the projection 32B received inthe groove 2A as shown in FIG. 4. The height of the first member 31 (thedistance between the lower end face of the annular protrusion 32A andthe top of the projection 31B) is set so that the second member 32 restson the projection 31B of the first member 31 and the brake gear 32A andthe stopper gear 23A are in mesh with each other so long as the secondmember 32 is in a position as urged by the coiled spring 10. Further theheight of the annular protrusion 31A of the first member 31 and thedepth of the annular groove 23C of the reel hub 23 are set so that theannular protrusion 31A is still in the annular groove 23C even if thefirst member 31 is lifted to its uppermost position. The first member 31and/or the second member 32 is formed of low friction, hardwearingmaterial such as polyoxymethylene, resin added with molybdenum or thelike.

In this state, rotation of the reel 4 is prevented by engagement betweenthe brake gear 32A and the stopper gear 23A. When the magnetic tapecartridge 1 is loaded in the recording and reproducing system, the brakerelease spindle of the recording and reproducing system pushes upwardthe exposed portion 31C of the brake member 30, whereby the first andsecond members 31 and 32 of the brake member 30 are moved upwardovercoming the force of the coiled spring 10 and the gears 32A and 23Aare disengaged from each other to permit rotation of the reel 4. At thistime, though the annular protrusion 31A of the first member 31 is movedupward relative to the annular groove 23C of the reel hub 23, theprotrusion 31A is not drawn out of the groove 23C as described above.

A tape outlet opening 26 through which the magnetic tape 20 is drawn outis formed in a side wall of the cartridge casing 7. The tape outletopening 26 is closed and opened by a slide door 27 which is slidable inthe directions of double-headed arrow A and is urged in the closingposition by a spring not shown.

A leader pin 21 is fixed to the leading end of the magnetic tape 20 andwhen the magnetic tape cartridge 1 is not used, the magnetic tape 20 isentirely wound around the reel 4 with the leader pin 21 held in a recess28 formed near the tape outlet opening 26.

When the magnetic tape cartridge 1 is loaded in a recording andreproducing system, the gears 23A and 32A of the hub 23 and the brakemember 30 are disengaged from each other to permit rotation of the reel4 in the manner described above and the drive mechanism of the recordingand reproducing system holds the reel plate 8 under magnetic force androtates the reel 4. At the same time, the slide door 27 is opened andthe leader pin 21 is brought to a predetermined position in a taperunning path, thereby recording or reproduction becomes feasible. Inthis state, since the annular protrusion 31A of the first member 31 isstill in the annular groove 23C, dust cannot enter the cartridge casing7 through the opening 23B of the reel hub 23.

Since the annular protrusion 31A is fitted in the annular groove 23C,the first member 31 is sometimes rotated relative to the second member32 in response to rotation of the reel 4. In this particular embodiment,since the first member 31 is in contact with only at the projection 31B,sliding resistance is small and generation of wear tailings can bereduced. Further since the first member 31 and/or the second member 32is formed of low friction, hardwearing material such aspolyoxymethylene, sliding resistance is smaller and generation of weartailings can be more reduced.

Though, in the first embodiment described above, the groove 23C isformed in the reel hub 23 and the protrusion 31A of the first member 31is fitted in the groove 23C, an annular wall portion 23D may be formedaround the opening 23B as shown in FIG. 5, and the annular protrusion31A may be fitted on the annular wall portion 23D. Otherwise an annularwall portion 23E may be formed around the opening 23B and the annularprotrusion 31A may be fitted in the annular wall portion 23E as shown inFIG. 6. In this case, it is preferred that an annular flange 23F beprovided to project inward from the annular wall portion 23E, therebypreventing the first member 31 from falling down through the opening23B.

Further, though, in the first embodiment described above, the firstmember 31 is in abutment against the second member 32 at the projection31B formed on the first member 31, such a projection may be formed onthe second member 32 or on each of the first and second members 31 and32.

A magnetic tape cartridge in accordance with a 20 second embodiment ofthe present invention will be described with reference to FIGS. 7 to 9,hereinbelow.

In FIG. 7, the magnetic tape cartridge 101 of the second embodimentcomprises a single reel 102 around which a magnetic tape (not shown) iswound and is contained for rotation in a cartridge casing 103. Thecartridge casing 103 is formed by fastening together upper and lowercasing halves 131 and 132 by screws and the like. The lower casing half132 is provided with a central opening 132 a. Further the magnetic tapecartridge 101 is provided with a reel stopper means 110 which preventsrotation of the reel 102 when the magnetic tape cartridge 101 is notused and permits rotation of the reel 102 when the magnetic tapecartridge 101 is used.

The reel 102 comprises a reel hub 121 which is a cylindrical memberhaving a bottom wall 121 a and doughnut-shaped lower and upper flanges122 and 123 extending outward from the lower and upper ends of the reelhub 121. The reel hub 121 and the lower flange 122 are formed integrallywith each other by molding of synthetic resin and the upper flange 123is fixed to the reel hub 121, for instance, by ultrasonic welding. Gearteeth (reel gear) 124 for driving the reel 102 are formed in a circle onthe lower surface of the bottom wall 121 a of the reel hub 121 and anannular reel plate 125 of magnetic metal is mounted on the lower surfaceof the bottom wall 121 a inside the reel gear 124. The reel gear 124 andthe reel plate 125 are exposed outside through the central opening 132 ain the cartridge casing 132. The reel 102 is urged downward by an urgingmember 105 to be described later.

A reel drive means 111 of a tape drive system comprises a rotary spindle112 provided with a drive gear 113 formed on the upper end face of therotary spindle 112 and a magnet disposed on the upper end face of thesame. When the magnetic tape cartridge 101 is loaded in the tape drivesystem, the rotary spindle 111 is moved upward toward the magnetic tapecartridge 101 and the drive gear 113 is brought into mesh with the reelgear 124 while the magnet attracts the reel plate 125 to hold the drivegear 113 in mesh with the reel gear 124.

The reel stopper means 110 comprises a brake member 104 which is movableup and down away from and toward the reel 102, an urging member 105which urges the brake member 104 toward the reel 102 and a brake releasemember 106 which moves the brake member away from the reel 102.

As shown in FIG. 8, three through holes 126 are formed in the bottomwall 121 a of the reel hub 121 at regular intervals on a circle toextend through the bottom wall 121 a at the portion where the reel gear124 is formed. Further three engagement projections 127 are erected fromthe upper surface of the bottom wall 121 a at regular intervals on acircle in positions angularly spaced from the through holes 126. Thenumber of the through holes 126 and the engagement projections 127 neednot be limited to three but for or more through holes 126 and engagementprojections 127 may be formed. The upper end portion of each engagementprojection 127 is shaped like a gear tooth and may be shaped like aplurality of gear teeth. In FIG. 8, only the bottom wall 121 a of thereel hub 121 is shown as the reel 102.

The brake member 104 is a substantially disc-like member and is disposedin the reel hub 121 opposed to the bottom wall 121 a of the reel hub121. A plurality of gear teeth 141 (stopper gear) are annularly formedon the lower surface of the brake member 104 and are adapted to bebrought into engagement with the engagement projections 127. A straightprotrusion 142 extends upward from the upper surface of the brake member104 and is fitted in a guide groove formed in a guide portion 131 aprojecting downward from the inner surface of the upper casing half 131,whereby the brake member 104 is able to be moved toward and away fromthe bottom wall 121 a of the reel hub 121 without rotating relative tothe reel hub 121. The protrusion 142 and the groove in the guide portion131 a may be like a cross in cross-section.

An urging member 105 in the form of a coiled spring compressed betweenthe upper surface of the brake member 104 urges the brake member 104toward the operative position where the stopper gear 141 and theengagement projections 127 are engaged with each other to preventrotation of the reel 104.

The brake release member 106 is disposed between the brake member 104and the bottom wall 121 a of the reel 25 hub 121 to be movable up anddown. As shown in FIG. 8, the brake release member 106 comprises acentral disc portion 161 and three arms 162 extending radially outwardfrom the central disc portion 161. A rectangular push rod 163 extendsdownward from the free end of each arm 162 and is inserted for up anddown movement into one of the through holes 126 formed in the bottomwall 121 a of the reel hub 121 with its lower end projected into teethportion of the reel gear 124 on the lower surface of the reel hub 121.The engagement projections 127 are positioned between the arms 162.

In the lowermost position of the brake release member 106 shown in FIG.7, the lower end face of each push rod 163 is positioned substantiallyflush with the tips of the teeth of the reel gear 124 and, in responseto chucking action of the rotary spindle 111 of the tape drive systemfor bringing the drive gear 113 into mesh with the reel gear 124, thepush rods 163 are pushed upward to move upward the brake release member106 by a predetermined amount, thereby disengaging the engagementprojection 127 from the stopper gear 141 to permit rotation of the reel102 as shown in FIG. 9. Since the push rods 163 are inserted into thethrough holes 126 in the reel hub 121, the brake release member 106 isrotated integrally with the reel 102.

The brake member 104 is urged downward by the 25 urging means 105 sothat the lower surface thereof abuts against the upper surface of thebrake release member 106. A spherical projection 164 is formed on theupper surface of the central disc portion 161 coaxially with the axis ofrotation of the brake release member 106, and a recess 143 having acurved bottom is formed on the lower surface of the brake member 104 sothat the tip of the spherical projection 164 abuts against the center ofthe recess 143. Further an annular protrusion 165 is formed on the uppersurface of the brake release member 106 around the spherical projection164 and the lower surface of the brake member 104 abuts against theupper surface of the protrusion 165. Thus the brake member 104 and thebrake release member 106 contact each other over a limited area, wherebythe resistance to rotation of the reel 102 is reduced and generation ofwear tailings can be suppressed.

As shown in FIG. 8, a plurality of slits 165 a are formed in the annularprotrusion 165 at predetermined intervals. Wear tailings generatedbetween the contact surfaces of the brake member 104 and the brakerelease member 106 are gathered in the slits 165 a so that the weartailings are not held between the contact surfaces to promote wear.

Though, in the embodiment described above, the projection 164 and theprotrusion 165 are formed on the brake release member 106, they may beformed on the brake member 104. Further only one of the projection 164and the protrusion 165 may be formed. Since the peripheral speedincreases toward the outer periphery of the central disc portion 161, itis preferred that the annular protrusion 165 be formed nearer to thecenter of the disc portion 161.

In the modification of the second embodiment shown in FIG. 10, the brakerelease member 106 contacts the brake member 104 at a ball 150 which ispress-fitted in a recess formed on the upper surface of the brakerelease member 106 and is received in a recess 144 formed in the lowersurface of the brake member 104. It is preferred that the ball 150 beformed hardwearing material such as steel or ceramics.

It is preferred that at least one of the brake member 104 and the brakerelease member 106 be formed of low friction, hardwearing material. Forexample, the brake member 104 is formed of polyoxymethylene while thebrake release member 106 is formed of polycarbonate resin, polycarbonateresin added with graphite, ABS resin, ABS resin added with graphite, ornylon resin added with molybdenum.

Further, as clearly shown in FIG. 8, the protrusion 142 extends longsubstantially across the upper surface of the brake member 104 andaccordingly the coiled spring 105 fitted on the protrusion 142 is largein diameter. That is, the coiled spring 105 acts on the brake member 104at a portion near the outer periphery of the brake member 104.Accordingly the coiled spring 105 acts on the brake member 104 at aportion near the push rods 163 which are pushed upward by the rotaryspindle 111 of the tape drive system. With this arrangement, deformationof the brake member 104, especially of the aims 162, can be suppressed,whereby the brake member 104 can be smoothly lifted without frictionbetween the outer surface of the push rod 163 and the inner surface ofthe through hole 126. Since the thickness of the brake member 104,especially of the arms 162, is restricted, the brake member 104 is aptto be deformed when the working point at which the coiled spring 105acts on the brake member 104 is remote from the working point at whichthe upward force transmitted from the rotary spindle 111 by way of thepush rods 163 acts on the brake member 104. When the brake member 104 isdeformed, the outer surface of the push rods 163 brought into contactwith the inner surface of the through holes 126 and frictiontherebetween adversely affects the brake release operation.

A magnetic tape cartridge in accordance with a third embodiment of thepresent invention will be described with reference to FIG. 11,hereinbelow.

The magnetic tape cartridge of the third embodiment is substantially thesame as the second embodiment, and accordingly the elements analogous tothose in the second embodiment are given the same reference numerals andonly the difference from the second embodiment will be mainly described.FIG. 11 is a view similar to FIG. 8 but showing the reel stoppermechanism in the third embodiment.

As shown in FIG. 11, in this embodiment, rotation of the reel 102 isprevented by engagement of an external bevel gear 141′ which is formedon the brake member 104 to conically taper toward the reel hub 121 andan internal bevel gear 127′ which is formed on the reel hub 121 toconically flare toward the brake member 104. The internal bevel gear127′ is partly cut away and the through holes 126 into which the pushrods 163 of the brake release member 106 are inserted are formed at thecutaway portions.

In this embodiment, since rotation of the reel 102 is prevented byengagement of the conical gears 141′ and 127′ and the former is pressedagainst the latter by the urging means, the brake member 104 is centeredwith respect to the reel hub 121 so that the center of the brake member104 is on the axis of rotation of the reel 102 and the gears 141′ and127′ are engaged with each other under a uniform pressure over theentire periphery thereof, whereby rotation of the reel 102 can be surelyprevented. Further for the same reason, the brake member 104 can belifted keeping the horizontal position by the spherical projection 164when the push rods 163 are pushed downward and the gear 141′ can besurely disengaged from the gear 127′ over the entire periphery thereof.

Rotation of the reel 102 may be prevented by pressing a high frictionconical surface on the brake member 104 against a high friction conicalsurface on the reel hub 121.

A magnetic tape cartridge in accordance with a fourth embodiment of thepresent invention will be described, hereinbelow.

As shown in FIG. 12, the magnetic tape cartridge 201 of the fourthembodiment comprises a single reel 202 around which a magnetic tape (notshown) is wound and is contained for rotation in a cartridge casing 203.The cartridge casing 203 is formed by fastening together upper and lowercasing halves 231 and 232 by screws and the like. The lower casing half232 is provided with a central opening 232 a. Further the magnetic tapecartridge 201 is provided with a reel stopper means 210 which preventsrotation of the reel 202 when the magnetic tape cartridge 201 is notused and permits rotation of the reel 202 when the magnetic tapecartridge 201 is used.

The reel 202 comprises a reel hub 221 which is a 20 cylindrical memberhaving a bottom wall 221 a and doughnut-shaped lower and upper flanges222 and 223 extending outward from the lower and upper ends of the reelhub 221. The reel hub 221 and the lower flange 222 are formed integrallywith each other by molding of synthetic resin and the upper flange 223is fixed to the reel hub 221, for instance, by ultrasonic welding. Gearteeth (reel gear) 224 for driving the reel 202 are formed in a circle onthe lower surface of the bottom wall 221 a of the reel hub 221 and anannular reel plate 225 of magnetic metal is mounted on the lower surfaceof the bottom wall 221 a inside the reel gear 224. The reel gear 224 andthe reel plate 225 are exposed outside through the central opening 232 ain the cartridge casing 232. The reel 202 is urged downward by an urgingmember 205 to be described later.

When the magnetic tape cartridge 201 is loaded in the tape drive system,the rotary spindle 111 is moved upward toward the magnetic tapecartridge 201 and the drive gear 113 is brought into mesh with the reelgear 224 while the magnet attracts the reel plate 225 to hold the drivegear 113 in mesh with the reel gear 224.

The reel stopper means 210 comprises a brake member 204 which is movableup and down away from and toward the reel 202, an urging member 205which urges the brake member 204 toward the reel 202 and a brake releasemember 206 which moves the brake member 204 away from the reel 202.

As shown in FIG. 13, three through holes 226 are formed in the bottomwall 221 a of the reel hub 221 at regular intervals on a circle toextend through the bottom wall 221 a at the portion where the reel gear224 is formed. Further three engagement projections 227 are erected fromthe upper surface of the bottom wall 221 a at regular intervals on acircle in positions angularly spaced from the through holes 226. In FIG.13, only the bottom wall 221 a of the reel hub 221 is shown as the reel202.

The brake member 204 comprises a disc-like member 241 disposed in thereel hub 221 opposed to the bottom wall 221 a of the reel hub 221. Aplurality of gear teeth 242 (stopper gear) are annularly formed on thelower surface of the disc-like member 241 and are adapted to be broughtinto engagement with the engagement projections 227. The lower surfaceof the disc-like member 241 is bulged downward at a central portionthereof and the central portion is brought into abutment against thecentral portion of the upper surface of a central disc portion (to bedescribed later) of the brake release member 206.

A protrusion 244 extends upward from the upper surface of the disc-likemember 241 of the brake member 204 and an engagement groove 245 shapedlike a cross in cross-section is formed in the protrusion 244. Anengagement projection 233 projecting downward from the inner surface ofthe upper casing half 231 is inserted into the engagement groove 245,whereby the brake member 204 is able to be moved toward and away fromthe bottom wall 221 a of the reel hub 221 without rotating relative tothe reel hub 221.

An urging member 205 in the form of a coiled spring compressed betweenthe upper surface of the brake member 204 urges the brake member 204toward the operative position where the stopper gear 242 and theengagement projections 227 are engaged with each other to preventrotation of the reel 204.

The brake release member 206 is disposed between the brake member 204and the bottom wall 221 a of the reel hub 221 to be movable up and down.As shown in FIG. 13, the brake release member 206 comprises a centraldisc portion 261 and three arms 262 extending radially outward from thecentral disc portion 261. A rectangular push rod 263 extends downwardfrom the free end of each arm 262 and is inserted for up and downmovement into one of the through holes 226 formed in the bottom wall 221a of the reel hub 221 with its lower end projected into teeth portion ofthe reel gear 224 on the lower surface of the reel hub 221. Theengagement projections 227 are positioned between the arms 262. The pushrod 263 may be circular or ellipsoidal in cross-section. The brakerelease member 206 may be shaped like a triangle with the push rods 263formed to extend downward at the corners of the triangle.

In the lowermost position of the brake release member 206 shown in FIG.12, the lower end face of each push rod 263 is positioned substantiallyflush with the tips of the teeth of the reel gear 224 and, in responseto chucking action of the rotary spindle 111 of the tape drive systemfor bringing the drive gear 113 into mesh with the reel gear 224, thepush rods 263 are pushed upward to move upward the brake release member206 by a predetermined amount, thereby disengaging the engagementprojection 227 from the stopper gear 241 to permit rotation of the reel202 as shown in FIG. 14. Since the push rods 263 are inserted into thethrough holes 226 in the reel hub 221, the brake release member 206 isrotated integrally with the reel 202.

The brake member 204 is urged downward by the urging means 205 so thatthe bulged central portion of the lower surface thereof is in slidingcontact with the upper surface of the brake release member 206.

Each of the through holes 226 formed in the reel hub 221 opens downwardat the portion of the lower surface of the reel hub 221 at which thereel gear 224 is formed in an area including at least a pair of opposedflanks of the reel gear 221 which form a valley of the reel gear 224.The through hole 226 may be of a rectangle, circle or ellipsoid or thelike according to the cross-sectional shape of the push rod 263.

For example, as shown in FIG. 15, the through hole 226 opens in a widthof one pitch of the reel gear 224 by cutting away a pair of flanks 224 abetween the tips 224 a of a pair of adjacent teeth. In this example, theopposed 25 flanks 224 a are inclined at the same angle and the center ofthe push rod 263 coincides with the center of the valley formed by theflanks 224 a and with the tip of a tooth of the drive gear 113 in meshwith the reel gear 224.

The through hole 226 should cover at least one valley and when eachvalley of the reel gear 224 is small because of a small diameter of thereel gear 224 or a small number of teeth, the through hole 226 isextended on one side or opposite sides of the valley as shown in FIGS.18 and 19 to be described later.

With this arrangement, even if the phase of the drive gear 113 isshifted from the phase of the reel gear 224 within one pitch when theformer is brought into mesh with the latter, the tip of a tooth of thedrive gear 113 can be surely brought into abutment against the lower endface of the push rod 263, whereby the push rod 263 can be surely liftedto disengage the stopper gear 242 from the engagement projections 227.

A recess 263 a which is adapted to be engaged with the tip of a tooth ofthe drive gear 113 may be formed on the lower surface of the push rod263 as shown in FIGS. 16A and 16B.

The tips 224 a of the teeth on opposite sides of the through hole 226may be cut flat at shown in FIG. 17. Otherwise such tips may be roundedor chamfered.

With this arrangement, generation of sharp edges by 25 cutting away apart of the reel gear 224 can be avoided, which facilitates formation ofthe mold for molding the reel hub 221 and facilitates molding of thereel hub 221.

In the modification shown in FIG. 18, the through hole 226 is wider thanone pitch of the reel gear 224 and is formed by cutting away a pair ofadjacent teeth from the root thereof with a pair of flat surfaces 24 cformed on opposite sides of the through hole 226.

In the modification shown in FIG. 19, the tip 224 a of each tooth of thereel gear 224 is flat on the outer portion and sharp on the innerportion and the height of the tooth becomes smaller toward the innerperiphery. Further the inclinations of the flanks on opposite sides ofeach valley differ from each other. The through hole 226 is wider thanone pitch of the reel gear 224 and is formed by cutting away a pair ofadjacent teeth from the root thereof with a pair of flat surfaces 24 cformed on opposite sides of the through hole 226.

FIGS. 20 and 21 show modifications of the brake release member 206. Inthese modifications, a blank in the form of a development of the brakerelease member 206 is stamped out from a sheet metal and the blank isbent into the brake release member 206. In the modification shown inFIG. 20, the blank has push rod portions extending in the longitudinaldirection of the portions forming the arms 262 and the push rod portionsare bent downward by 90° to form the push rods 263. The tip portion ofeach of the push rod portions is further bent to form an abutmentportion 263 b on the lower end of the push rod 263. In the modificationshown in FIG. 21, the blank has push rod portions extending laterallyfrom the ends of the portions forming the arms 262 and the push rodportions are bent downward by 90° to form the push rods 263. The tipportion of each of the push rod portions is further bent to form anabutment portion 263 b on the lower end of the push rod 263.

By thus forming the brake release member 206 of sheet metal, the brakerelease member 206 can be sufficiently rigid for its thickness.

It is preferred that the push rod 263 be arranged so that the push rod263 contacts with the inner surface of the through hole 226 at fineprotrusions formed on the outer surface of the push rod 263 or on theinner surface of the through hole 226 to extend in the longitudinaldirection of the push rod 263 in order to reduce the contact areatherebetween.

In the example shown in FIG. 22A, the push rod 263 is square incross-section and a plurality of protrusions 226 a are formed on theinner surface of the through hole 226 to extend in the longitudinaldirection of the push rod 263, whereby the push rod 263 contacts withthe inner surface of the through hole 226 only at the protrusions 226 a.In the example shown in FIG. 22B, a plurality of protrusions 263 d areformed on the outer surface of the push rod 263 to extend in thelongitudinal direction of the push rod 263.

In the examples shown in FIGS. 23A and 23B, the push rod 263 is circularin cross-section, a plurality of protrusions 226 a are formed on theinner surface of the through holes 226.

In the examples shown in FIGS. 22A, 22B, 23A and 23B, the protrusions226 a and 263 d are about several tens μm though exaggerated in thedrawings.

A magnetic tape cartridge 301 in accordance with a 10 fifth embodimentof the present invention will be described with reference to FIGS. 24and 25, hereinbelow. The magnetic tape cartridge 301 of this embodimentdiffers from that of the second embodiment mainly in the structure ofthe reel stopper means, and accordingly only the structure of the reelstopper means will be mainly described.

As shown in FIGS. 24 and 25, in this embodiment, the reel stopper means310 comprises a brake member 304 which is movable up and down away fromand toward the reel 302, an urging member 305 which is formed integrallywith the brake member 304 and urges the brake member 304 toward the reel302 and a brake release member 306 which moves the brake member awayfrom the reel 302.

As shown in FIG. 25, three through holes 326 are formed in the bottomwall 321 a of the reel hub 321 at regular intervals on a circle toextend through the bottom wall 321 a at the portion where the reel gear324 is formed. Further three engagement projections 327 are erected fromthe upper surface of the bottom wall 321 a at regular intervals on acircle in positions angularly spaced from the through holes 326. Theupper end portion of each engagement projection 327 is tapered. In FIG.8, only the bottom wall 321 a of the reel hub 321 is shown as the reel302.

The brake member 304 is formed by a plate material and has a centraldisc portion 341 convex upward and concave downward and three arms 342extending radially outward from the disc portion 341. The free endportion of each arm 342 is bent downward to form a pair of engagementportions 343 which forms an engagement recess in which the tip of theengagement projection 327 is fitted to prevent rotation of the reel 302.Three spring plates 305 extend radially outward from the disc portion341 between the arms 342.

An annular holding portion 333 extends downward from the inner surfaceof the upper casing half 331. Three first recesses 333 a are formed onthe lower end face of the holding portion 333 at regular intervals andthree second recesses 333 b are formed on the lower end face of theholding portion 333 between the first recesses 333 a. The first recesses333 a are deeper than the second recesses 333 b and the free endportions of the arms 342 are inserted into the first recesses 333 a tobe movable up and down. The free end portions of the plate springs 305are engaged in the second recesses 333 b.

With this arrangement, the brake member 304 is able to be moved towardand away from the bottom wall 321 a of the reel hub 321 without rotatingrelative to the reel hub 321, and is urged toward the reel hub 304 bythe plate springs 305.

The brake release member 306 is disposed between the brake member 304and the bottom wall 321 a of the reel hub 321 to be movable up and down.As shown in FIG. 25, the brake release member 306 comprises a centraldisc portion 361 and three arms 362 extending radially outward from thecentral disc portion 361. A rectangular push rod 363 extends downwardfrom the free end of each arm 362 and is inserted for up and downmovement into one of the through holes 326 formed in the bottom wall 321a of the reel hub 321 with its lower end projected into teeth portion ofthe reel gear 324 on the lower surface of the reel hub 321. Theengagement projections 327 are positioned between the arms 362.

A spherical projection 364 is formed on the upper surface of the centraldisc portion 361 and is in contact with the lower concave surface of thecentral disc portion 341.

In the lowermost position of the brake release member 306 shown in FIG.24, the lower end face of each push rod 363 is positioned substantiallyflush with the tips of the teeth of the reel gear 324 and, in responseto chucking action of the rotary spindle 111 of the tape drive systemfor bringing the drive gear 113 into mesh with the reel gear 324, thepush rods 363 are pushed upward to move upward the brake release member306 by a predetermined amount, thereby disengaging the engagementprojection 327 from the engagement portions 343 to permit rotation ofthe reel 302. Since the push rods 363 are inserted into the throughholes 326 in the reel hub 321, the brake release member 306 is rotatedintegrally with the reel 302.

In this embodiment, since the brake member 304 and the urging means 305are integral with each other, the number of parts can be reduced andassembly of the magnetic tape cartridge is facilitated.

A magnetic tape cartridge 401 in accordance with a sixth embodiment ofthe present invention will be described with reference to FIGS. 26 and27, hereinbelow. The magnetic tape cartridge 401 of this embodimentdiffers from that of the second embodiment mainly in the structure ofthe reel stopper means, and accordingly only the structure of the reelstopper means will be mainly described.

As shown in FIGS. 26 and 27, in this embodiment, the reel stopper means410 comprises a brake release member 404 which is rotatable integrallywith the reel 402 and is movable up and down away in response tochucking operation of the rotary spindle 111 of the tape drive system, abrake member 405 which is fixed to the cartridge casing 403 and isbrought into engagement with a part of the brake release member 404 toprevent rotation of the reel 402, and urging members 406 which urges thebrake release member 404 toward the position where it engages with thebrake member 405.

As shown in FIG. 27, three through holes 426 are formed in the bottomwall 421 a of the reel hub 421 at regular intervals on a circle toextend through the bottom wall 421 a at the portion where the reel gear424 is formed. Further three spring retainer projections 427 are formedon the inner peripheral surface of the reel hub 421 at regular intervalsin positions angularly spaced from the through holes 426 as shown inFIG. 26. Each spring retainer portion 427 is provided with a recess intowhich the base portion of a plate spring 406 (urging member) is insertedas will be described later. In FIG. 27, only the bottom wall 421 a ofthe reel hub 421 is shown as the reel 402.

The brake member 405 comprises a disc portion 451. 20 A stopper gear 452is formed on the upper surface of the disc portion 451 along the outerperiphery thereof and a projection 453 extends upward at the centralportion of the disc portion 451. The projection 453 is fixed in anannular recess 431 a formed on the inner surface of the upper casinghalf 431, whereby the brake member 405 is fixed to the cartridge casing403 not to be rotatable. The brake member 405 is disposed inside thereel hub 421 opposed to the bottom wall 421 a thereof.

The brake release member 404 comprising an annular portion 441 providedwith a central opening. A brake gear 442 (FIG. 26) which is adapted tobe engaged with the stopper gear 452 is formed on the lower surface ofthe annular portion 441. The brake release member 404 is disposed abovethe brake member 405 to be movable up and down with the projection 453of the brake member 405 extending through the central opening of theannular portion 441. Three rectangular push rods 443 extend downwardfrom the outer periphery of the annular portion 441 and are inserted forup and down movement into the through holes 426 formed in the bottomwall 421 a of the reel hub 421 with its lower end projected into teethportion of the reel gear 424 on the lower surface of the reel hub 421.

Each of the plate springs 406 comprises a vertical base portion and acurved resilient arm portion. The plate spring 406 is mounted on thereel hub 421 by inserting the base portion into the spring retainerportion 427 with the resilient arm portion in abutment against the uppersurface of the annular portion 441 of the brake release member 404.

In the lowermost position of the brake release member 404 shown in FIG.26, the lower end face of each push rod 443 is positioned substantiallyflush with the tips of the teeth of the reel gear 424 and, in responseto chucking action of the rotary spindle 111 of the tape drive systemfor bringing the drive gear 113 into mesh with the reel gear 424, thepush rods 443 are pushed upward to move upward the brake release member404 by a predetermined amount, thereby disengaging the stopper gear 452from the brake gear 442 to permit rotation of the reel 402. Since thepush rods 443 are inserted into the through holes 426 in the reel hub421, the brake release member 404 is rotated integrally with the reel402. In this embodiment, since the brake release member 404 is rotatedwithout contacting the brake member 405, resistance to rotation of thereel 402 is reduced and generation of wear tailings is prevented.

In the embodiments described above, it is preferred that the brakerelease member be formed of fiber reinforced resin such as long-fiberreinforced resin, carbon fiber reinforced resin and the like. Such fiberreinforced resin comprises polyamide resin, polyoxymethylene,polycarbonate, ABS resin, polybutylene terephthalate and the like addedwith glass fiber, carbon fiber, boron fiber, silicon carbide fiber,alumina fiber and the like.

Further it is preferred that the brake member and/or the brake releasemember be formed of synthetic resin containing therein lubricant such asmolybdenum, polytetrafluoroethylene, graphite, potassium titanatewhisker, silicone formed of dimethyl polysiloxane of various grades andmodifications thereof and the like.

In addition to the lubricant listed above, amide oleate lubricant,ercuamide lubricant, amide stearate lubricant, bis-aliphatic acidlubricant, nonionic surface active agent lubricant, hydrocarbonlubricant, aliphatic acid lubricant, ester lubricant, alcohol lubricant,metal soap and the like may be added.

As the synthetic resin, polycarbonate, polyoxymethylene, PPS, aliphaticpolyamide such as nylon 6, nylon 66(6,6;6/6) and the like, aromaticpolyamide, ultra-high-molecular-weight polyethylene, isotacticpolypropylene, syndiotactic polystyrene, and hardwearing resin having animide group such as polyimide, polyamide-imide, polyether imide and thelike are preferred.

What is claimed is:
 1. A magnetic tape cartridge comprising a cartridgecasing, a single reel around which a magnetic tape is wound and which iscontained in the cartridge casing for rotation, and a brake means whichis movable between an operative position where it prevents rotation ofthe reel and a retracted position where it permits rotation of the reel,wherein the brake means comprises a brake member which is disposed inthe cartridge casing not to be rotatable and is movable between anoperative position where it engages with the reel to prevent rotation ofthe reel and a retracted position where it is disengaged from the reelto permit rotation of the reel, an urging means which urges the brakemember toward the operative position, and a brake release member whichis disposed in the cartridge casing to be rotated together with the reeland moves the brake member to the retracted position in response tochucking operation of a tape drive mechanism of a tape drive system,said brake member having an engagement surface which is conicallyinclined with respect to the axis of rotation of the reel and is broughtinto engagement with a complementary surface formed on the reel toprevent rotation of the reel when the brake member is moved to theoperative position, and said brake member being automatically centeredwith respect to a reel hub.
 2. The magnetic tape cartridge as defined inclaim 1, wherein the brake release member is formed of fiber reinforcedresin.
 3. The magnetic tape cartridge as defined in claim 1, wherein atleast one of the brake release member and the brake member is formed ofsynthetic resin containing therein lubricant selected from the groupconsisting of molybdenum, polytetrafluoroethylene, graphite, potassiumtitanate whisker, and silicone formed of dimethyl polysiloxane.
 4. Themagnetic tape cartridge as defined in claim 2, wherein said fiberreinforced resin is one of long-fiber reinforced resin and carbon fiberreinforced resin.